Protective proteins are differentially expressed in tomato genotypes differing for their tolerance to low-temperature storage.

When stored at low temperature, tomato fruits exhibit chilling injury symptoms, such as rubbery texture and irregular ripening. To identify proteins related to chilling tolerance, we compared two tomato near isogenic lines differing for their texture phenotype at harvest in a fruit-storage trial including two temperatures (4 and 20 degrees C) along several days of conservation. Fruit evolution was followed by assessing fruit color, ethylene emission and texture parameters. The most contrasted samples were submitted to proteomic analysis including two-dimensional electrophoresis and mass spectrometry of protein spots to identify the proteins, whose expression varied according to the genotype or the storage conditions. Unexpectedly, the most firm genotype at harvest was the most sensitive to cold storage. The other genotype exhibited a delay in fruit firmness loss leading to the texture differences observed after 20 days of 4 degrees C storage. The proteome analysis of these contrasted fruits identified 85 proteins whose quantities varied with temperature or genotype. As expected, cold storage decreased the expression of proteins related to maturation process, such as acidic invertase, possibly controlled post-translational regulation of polygalacturonase and up-regulated proteins related to freezing tolerance. However, the study point out proteins involved in the differential resistance to chilling conditions of the two lines. This includes specific isoforms among the large family of small heat shocked proteins, and a set of proteins involved in the defense against of the reticulum endoplasmic stress.

Two-dimensional electrophoretic analysis of proteins associated with somatic embryogenesis development in Cupressus sempervirens L.

Two-dimensional gel electrophoretic analysis and histological studies were performed on somatic embryos in cypress. Embryogenic cultures were obtained from in vitro culture of immature seeds. On a modified Murashige and Skoog (MS) medium they showed an intense and repetitive cleavage polyembryogenesis phenomenon which maintained them in a continuous proliferating status instead of undergoing a complete embryogenic development. Only the addition of bovine serum albumin to the culture allowed somatic embryo development and maturation. Major histological differences were noticed between developing and nondeveloping embryogenic cultures. Attempts to find proteins that could be associated with developmental stages of somatic embryos have been achieved. Proteins were extracted and analyzed by two-dimensional electrophoresis from nondeveloping embryogenic cultures (S0) and from embryogenic cultures at three different stages of somatic embryo development: small size and rounded shape embryos (S1), increased size embryos with a well-developed suspensor (S2) and embryos with two well-separated cotyledons (S3). The results revealed some qualitative and quantitative protein variations between the two cultures. Some could be connected with the induction of pro-embryo differentiation whereas others should be more related to the mechanisms involved in somatic embryo development and maturation. Specific polypeptides associated with the presence of bovine serum albumin (BSA) in the medium have been detected.

Application of two-dimensional gel electrophoresis to Prunus armeniaca leaf and bark tissues.

The protein composition of Prunus armeniaca bark and leaf tissues was investigated by two-dimensional gel electrophoresis. Three different extraction procedures were tested in order to obtain reproducible gels with numerous spots of high intensity. The best results were achieved with extraction in Tris-buffer in the presence of a nonionic detergent, reducing agents, and polyphenol oxidase inhibitors. As many as 744 protein spots were resolved from leaf tissues. The patterns exhibited well-focused spots, with apparent molecular masses ranging from 19 to 90 kDa and isoelectric point from 4.5 to 8.5. The Tris extraction buffer was also the most appropriate for cortical tissue analysis.